The background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
Point-of-care analytical devices have increasingly become an attractive option in physician's offices and homes as a way to decrease patient costs and increase the speed of test results and disease diagnosis. These devices offer many advantages over the use of traditional laboratories for conducting tests and diagnosing diseases. For example, support staff can operate analytical devices with minimal training and can perform various in vitro diagnostic tests on blood (serum and/or plasma), urine, cerebrospinal fluid or other biological fluids in a matter of minutes while a patient waits.
Despite their many advantages, point-of-care analytical diagnostic devices generally can be prone to errors. For example, human errors, such as errors in sample extraction, pipetting, etc., can cause problems with the analysis by introducing variations in the tested sample volumes. In addition, most point-of-care devices are insensitive to changes in sample quality, integrity, and composition (e.g. from hemolysis of blood) that can also decrease the accuracy of these devices.
U.S. Patent Application US 2015/0086970 to Poirier describes a whole blood analytic device with many of the advantages described above. These and all other extrinsic materials discussed herein are incorporated by reference in their entirety. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply. Poirier describes an analytical device with a solid porous structure that separates a blood containing fluid for analysis. However, the device does not positively determine the sample volume to be analyzed, but relies on the assumption that the solid porous structure is saturated. Moreover, the device is unable to detect flaws in the solid porous structure, detect when insufficient sample is added, or detect errors in the integrity of the sample, such as hemolysis.
Some effort has been made to improve the accuracy of these devices. For example, U.S. Pat. No. 6,060,320 to Dorenkott and Panek describes a method of verifying the volume of an aspirated liquid in an automatic diagnostic system. The system in Dorenkott and Panek determines volume from the pressure needed to aspirate the liquid. However, although the system in Dorenkott and Panek can detect volume of a sample, it is expensive and suffers from a number of deficiencies that make it less ideal in a point-of-care setting.
U.S. Pat. No. 7,247,483 to Halg et al. describes a method for determining the volume of a sample of a liquid by the addition of a chromophore to the sample. The volume of the sample can be determined by measuring the chromophore concentration in the sample, however, this approach still leaves room for human error and may interfere with downstream assays, especially assays based on colorimetric of fluorescence signal.
U.S. Patent Application US 2012/0309636A1 to Gibbons et al. teaches systems, devices and methods for the automatic detection of analytes in a bodily fluid. The system and methods in Gibbons et al. use a light source and a camera to measure and verify sample volume in a pipette tip or cuvette. However, especially at relatively small volumes, errors can readily occur due to variations in surface tension, presence of air bubbles, and incomplete wetting of the sample to the pipette tip. Still further, Gibbons et al. require measurement of absorbance, which can be affected by one or more analytes in the sample having similar absorption characteristics.
Therefore, even though various methods and systems for sample measurement are known in the art, all or all of them suffer from one or more disadvantages. Thus, there is a need for improved sample verification systems and methods in analytical diagnostic devices.